When you buy a new condo from a builder, you may not legally own it when you think you do.

Most people think that once their condo is built and they have their key in hand, they are the legal owner. This is not necessarily the case. The day you get the key may be the first day of what is known as interim occupancy. You will be a registered owner on title only when the condominium development declares itself a condominium corporation.

What is interim occupancy? It’s the interval between the day you take possession of your purchased condo unit and the day the condo developer actually declares the condo a registered condominium.

This interval may be anywhere from days to months, and occasionally six months or longer. Cathedral Hill, for example, has already been occupied by many owners but is not yet a registered condominium. It’s expected it will be registered by the end of August, yet some residents took their interim occupancy in May.

What does that mean for the owners? They pay fees to the builder to cover estimated taxes and estimated condo fees and interest. During interim occupancy, owners typically move into units on lower floors first and, as the builder continues to construct higher into the sky, owners of condos on higher floors may take occupancy.

Interim occupancy is also the period during which owners list any deficiencies and point them out to the builder so that they may be fixed before the development is completed. During this time, the builder will have the right to enter your condo to assess and address your concerns. For some early occupiers, this may be quite disruptive and annoying, plus living on a construction site means dust, noise and dirt may invade your living space.

On the other hand, some buyers actually enjoy living in a condo construction site. It certainly can be exciting to see the evolution of the project. After all, condo developments typically take a year or two from public release to move-in time, during which they may be associated with plenty of hype.

The residents at Brad Lamb’s Gotham are among those who are living in a nearly finished condo. One owner decided to purchase their unit after a two-year search. They ultimately chose the building in part because it’s well located downtown on Lyon Street. One of the things they loved is that it has few amenities, meaning they won’t pay condo fees for features they won’t use.

Unfortunately, they are relocating and may post their condo for sale during the interim occupancy period. Many condo developments will not allow purchasers to list their units for sale until the condominium is a registered corporation. But in this case, because the condo project was delayed, the developer gave them the go-ahead to sell. Gotham is now scheduled to be finished by October.

Delays can occur with even the most prestigious developers, often for reasons that are beyond their control. As a result, interim occupancy is a not unusual issue. The most important thing to do if considering interim occupancy is to discuss buyer obligations with your lawyer. These will include estimated condo fees and taxes, interest payable on the balance of the purchase price as well as any other caveats such as the right to sell during interim occupancy, consequences of not completing the development on schedule, etc. That way you are less likely to encounter unpleasant surprises.

Marilyn Wilson has been selling real estate for more than 25 years and owns Marilyn Wilson Dream Properties Inc. Christie’s International Real Estate. Reach her through dreamproperties.com.